For example, in a system, such as a portable telephone and some digital cameras, which enables the charge of the apparatus with a secondary battery remaining being loaded therein, it is general that a charge and discharge circuit 5 is provided with a bidirectional regulator circuit 120 as shown in FIG. 19, and that the bidirectional regulator circuit 120 adjusts a current and a voltage at the time of charge and discharge. Moreover, the switching between the charge operation and the discharge operation of the bidirectional regulator circuit 120 is generally performed based on the switched states of the terminals for the connection with a power source device 2 and set equipment 3 of a power supply destination. That is, if the power source device 2 is connected to the charge and discharge circuit 5 based on the switched state of a terminal connection switching circuit 110, then the bidirectional regulator circuit 120 is made to perform a charge operation; and if the power source device 2 is not connected, then the bidirectional regulator circuit 120 is made to perform a discharge operation.
Moreover, the following techniques were disclosed as the related art of the present invention. For example, Patent publication 1 disclosed the technique of performing the charge of an auxiliary power source (secondary battery) by the use of a bidirectional converter when the electric power of a main power source was superfluous, and of performing the discharge of the auxiliary power source at the starting time of a system, when the electric power of the main power source was insufficient, in a power source device for performing power supply from the main power source and the auxiliary power source.
Moreover, Patent Publication 2 disclosed the technique of connecting a bidirectional converter at the preceding stage of a battery to make the bidirectional converter perform a charge operation and a discharge operation based on a discharge instruction and a charge instruction in a photovoltaic power generating provision connecting a solar cell, the battery, and a load with one another.
Moreover, Patent Publication 3 disclosed a bidirectional converter to perform the charge of a battery as a step-down chopper circuit at the time of charge, and to perform the discharge of the battery as a step-up chopper circuit at the time of discharge.    Patent Publication 1: Japanese Laid-Open Publication No. H6-245543    Patent Publication 2: Japanese Patent Application No. H5-055467    Patent Publication 3: Japanese Laid-Open Publication No. 2003-304644